The present invention relates to an improved regulator for automatically regulating the power applied to a load such as a lamp to a predetermined value. The regulator is especially suited, but not limited to application for regulating the power applied to a document illumination lamp in an electrostatic copying machine.
Variations in the power applied to such a lamp causes variation of the luminous intensity of the lamp and thereby the density of a copy produced by the electrostatic copying machine. Short term variations caused by power supply fluctuations and the like cause localized uneven copy density in a single copy. Many attempts to provide precise regulation of lamp power have been made in an attempt to eliminate this obviously undesirable phenomenon, but none of these efforts have heretofore proven completely successful.